The present invention relates to a nozzle head for subjecting a surface of a substrate to successive surface reactions of at least a first precursor and a second precursor, and particularly to a nozzle head according to the preamble of claim 1. The present invention further relates to a an apparatus comprising a nozzle head for subjecting a surface of a substrate to successive surface reactions of at least a first precursor and a second precursor, and particularly to an apparatus according to the preamble of claim 17. The present invention also relates to a method for subjecting a surface of a substrate to successive surface reactions of at least a first precursor and a second precursor, and particularly to a method according to the preamble of claim 25.
In the prior art several types of apparatuses, nozzle heads and nozzles are used for subjecting a surface of a substrate to successive surface reactions of at least a first precursor and a second precursor according to the principles of atomic layer deposition method (ALD). In ALD applications, typically two gaseous precursors are introduced into the ALD reactor in separate stages. The gaseous precursors effectively react with the substrate surface, resulting in deposition of a growth layer. The precursor stages are typically followed or separated by an inert-gas purge stage that eliminates the excess precursor from the surface of the substrate prior to the separate introduction of the other precursor. Therefore an ALD process requires alternating in sequence the flux of precursors to the surface of the substrate. This repeated sequence of alternating surface reactions and purge stages between is a typical ALD deposition cycle.
The prior art apparatuses for continuously operating ALD usually comprise a nozzle head having one or more first precursor nozzles for subjecting the surface of the substrate to the first precursor, one or more second precursor nozzles for subjecting the surface of the substrate to the second precursor, one or more purge gas channels and one or more discharge channels for discharging both precursors and purge gas arranged in the following order: at least a first precursor nozzle, a first discharge channel, purge gas channel, a discharge channel, a second precursor nozzle, a discharge channel, a purge gas channel and a discharge channel, optionally repeated a plurality of times. The problem with this prior art nozzle head is that it comprises several different nozzles and channels which makes the nozzle head complicated and rather large. The nozzle is preferably moved in relation to the substrate for producing a number of growth layers.
Another type of prior art nozzle head for continuous ALD comprises alternatively in succession: a first precursor nozzle, a purge gas channel, a second precursor nozzle and purge gas channel, optionally repeated a plurality of times. In this prior art nozzle head each of the precursor nozzles and purge gas channels is provided with an inlet port and an outlet port such that the precursor and the purge gas is both supplied and discharged using the same nozzle. Therefore there are no separate discharge channels. The problem with this prior art nozzle head is that purge gas will leak to the precursor nozzle such that the precursor concentration will dilute. Thus the nozzle head is unable to provide a uniform gas supply over the whole length of the precursor nozzle or over the whole output face of the nozzle head. Furthermore the construction is complicated as there are inlet port and outlet port in each of the nozzles. Also this nozzle head may be moved relative to the substrate for producing a number of growth layers.